When sniffing the network traffic, discard class D and E IP addresses when sniffing traffic. This was a reason why filters were not correctly rebuilt on VMs on the local 192.* network when libvirt was restarted and those VMs did not use a DHCP request to get its IP address. Signed-off-by: Stefan Berger <stefanb(a)us.ibm.com&gt; --- src/nwfilter/nwfilter_learnipaddr.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) Index: libvirt-acl/src/nwfilter/nwfilter_learnipaddr.c =================================================================== --- libvirt-acl.orig/src/nwfilter/nwfilter_learnipaddr.c +++ libvirt-acl/src/nwfilter/nwfilter_learnipaddr.c @@ -546,9 +546,12 @@ learnIPAddressThread(void *arg) struct iphdr *iphdr = (struct iphdr*)(packet + ethHdrSize); vmaddr = iphdr->saddr; - // skip eth. bcast and mcast addresses, + // skip eth. bcast and mcast addresses (224.0.0.0 - + // 239.255.255.255), class E (255.*) // and zero address in DHCP Requests - if ((ntohl(vmaddr) & 0xc0000000) || vmaddr == 0) { + if ( (ntohl(vmaddr) & 0xe0000000) == 0xe0000000 || + (ntohl(vmaddr) & 0xf0000000) == 0xf0000000 || + vmaddr == 0) { vmaddr = 0; continue; }